1. Field of the Invention
This invention relates to a novel process for producing copolymers using homopolymers as the starting materials. More specifically, this novel process involves reacting a mixture of two or more polyamides, especially poly(caproamide) (nylon 6) and poly(hexamethylene adipamide) (nylon 6,6) and one or more aryl phosphoryl azide compounds in order to obtain a copolymer from the reaction of the individual homopolymers. The materials obtained by this process are not strictly random or block copolymers but behave similarly to a random system and, therefore, we classify them as "quasi-random" copolymers. For simplicity, we shall refer to them as random copolymers. The random copolymers of the present invention may be fabricated into films or other products which have desirable properties, and can be useful in making injection molded or extruded products of improved properties.
2. Description of the Prior Art
U.S. Pat. No. 4,417,032 discloses a process for forming quasi-random copolymers from two or more homo polyamides. In this process, the homo polyamides are melt blended in the presence of a phosphite promoter.
U.S. Pat. No. 3,509,107 discloses a process for increasing the relative viscosity of polyamide fibers or copolyamides by incorporating a phosphorous or phosphite compound into the polyamide under an inert gas atmosphere. The primary object of U.S. Pat. No. 3,509,107 is to provide a process for increasing the viscosity of polyamide yarn and cord which requires a minimum amount of gas. U.S. Pat. No. 3,551,548 (Brignac et al., 1970) describes various optimizing procedures for U.S. Pat. No. 3,509,107. The described patents are each directed only to a method of producing polyamide yarn with increased viscosity via incorporating a phosphorous or phosphite compound into the yarn, and then heating said yarn in the presence of inert gas.
British Patent No. 569,184 discloses a method for producing a random copolymer from nylon 6 and nylon 6,6. The invention described herein teaches that heating a mixture of nylon 6 and nylon 6,6 results in interchange between various sections of the respective polymer molecules with the final product being a random copolymer of nylon 6 and nylon 6,6. In order to produce a random copolymer of nylon 6 and nylon 6,6, British Patent No. 569,184 teaches that it is necessary to heat the mixture of homopolymers for periods of time up to 8 hours at 285.degree. C. without any catalyst.
U.S. Pat. No. 4,390,667 discloses a process for decreasing the melt index and increasing the viscosity of polyamide fibers via incorporating a phosphate compound into the polyamide and heating the polylamide until the desired changes in the melt index and viscosity occur. The phosphate utilized in U.S. Pat. No. 4,390,667 include substituted aryl phosphates which satisfy certain Hammett sigma values.
U.S. Pat. No. 4,417,031 discloses a process for preparing block and graft copolymers. The described process involves reacting two or more polyamides, polyesters, and homopolymers of .beta.-unsaturated carboxylic acids in order to form a graft and/or block copolymer. Included in the patent are copolymers formed from poly(caproamide) and poly(hexamethylene adipamide).
Diphenyl phosphoryl azide has been used as a convenient reagent for racemization-free peptide synthesis and for polymerization of peptides such as .beta.-alamino and L-alanylglycine. See for example, Nishi, Noro et al. "Polymerization of Amino-acids or Peptides with Diphenyl Phosphoryl Azide (DPPA)", Int. J. Biol. Macromol., Vol. 2, p. 53 (1980) and Shiori, Takayuki, "Diphenylphosphoryl Azide. A New Convenient Reagent for a Modified Curtius Reaction and for the Peptide Synthesis", J. of the American Chemical Society, Vol. 94, p. 6203-6205 (1972).